1. Field of the Invention
This invention relates to the field of commercial video displays.
Large video displays, produced by a number of individual display units arranged in a matrix, are used commercially for a variety of purposes, such as retail displays, electronic billboard advertising, scoreboard displays in sports arenas, or showing films or television programs to an audience. The signals to the individual displays are typically provided via a computer and specialized software which allows the image to be displayed and manipulated in a variety of intriguing ways, e.g. zooming in and out, splitting the image, displaying unrelated images on different individual units, displaying related images which combine to form a larger image, etc.
One disadvantage of using conventional television-type displays is that the screens are curved at their edges, producing large "black" areas between individual screens. Projection televisions have therefore become the display of choice, since they permit rectangular images to be presented. Even with projection units, however, there are black lines or borders between individual units. It is highly desirable to reduce the width of these borders as much as possible.
Rear projection systems are commonly used in such displays, but are quite deep. It is often desirable to have a display with much less depth, which can be achieved using a video projector mounted in a housing to project upwardly, with a mirror to direct the image forwardly onto a viewing screen.
2. Description of the Prior Art
Large video displays using video projectors are already known. Most use direct rear projection rather than mirror-reflected rear projection. Examples are the displays sold as Electrosonic Profile by Electrosonic Systems, Inc. of Minneapolis, Minn., and the Pioneer RM-V2000A system sold by Pioneer Electronic Corporation of Japan.
At least one system, sold by Hitachi and described as its Model CM100 100-inch Presentation System, uses mirror-reflected projection in a fixed 2.times.2 unit.